The Corncob Car…

…uses carbon briquettes made from corncobs to store methane, the main component in natural gas, at a density of 180 times their volume and at one seventh the pressure of conventional methane gas tanks. The storage system is the first to meet the U.S. Department of Energy’s storage density target of 180-to-1 by volume, set in 2000, said Peter Pfeifer, principal project leader and professor of physics at University of Missouri, Columbia.
The storage system also allows methane to be stored at a lower pressure of 500 pounds per square inch – the same as in natural gas pipelines—helping car makers fashion fuel tanks in any shape.

Current technology relies on large cylindrical tanks that compress natural gas to a pressure of 3600 pounds per square inch. And that can take up an entire trunk. (redherring.com)

Unlike some alternative fuels like hydrogen, natural gas is available anywhere. However, using a heavily traded commodity and placing a further demand on natural gas would probably cause a sharp increase in price